I’ve been noticing a lot of issues with GPS on my FP4 recently.
It’s particularly noticable when tracking an activity like cycling, that whole stretches of the (not particularly shaded) route are missing, or have the location jumping around wildly.
In the Google Maps app I noticed at one point that the device seemed to have the correct location for me, but every few seconds it would jump to a location ~100m away, then jump back, and keep doing that. Rebooting the phone “fixed” that issue temporarily.
Comparing my FP4 with FP5, the FP4 has a lot issues. Often when using GMaps it has my location, I search a route and start navigation and then GPS is lost and it takes minutes to get a fix and after that it works.
I have a similar problem. I bought a Fairphone in January 2024 and the GPS worked properly till September 2024. Since this month the performance os poorer. The location is lost when entering even in open forests.